1. Field of the Invention
The present invention relates to a method of producing a magnetic garnet single crystal film.
2. Description of the Related Art
Conventionally, magnetic garnet single crystal films are widely used for magnetostatic wave devices such as a delay line filter, an oscillator, a nonlinear device, and the like, and for magnetooptical devices such as an optical isolator using a Faraday rotation effect, a circulator, and the like. As a main method of producing such magnetic garnet single crystal films, a liquid phase epitaxial growth process (LPE process) is known.
The liquid phase epitaxial growth process for producing a magnetic garnet single crystal film comprises, for example, filling a platinum crucible maintained in a heating furnace with oxides of constituent elements of garnet and PbO and B2O3 as a flux, and homogenizing at about 1200xc2x0 C. to form a melt. Next, the melt is maintained in a supercooled state, i.e., at a temperature (about 900xc2x0 C.) below and near the liquid line, and, for example, a Gd3Ga5O12 (referred to as xe2x80x9cGGGxe2x80x9d hereinafter) substrate as a base substrate is then immersed in the melt, followed by epitaxial growth for a predetermined time to grow a magnetic garnet single crystal film on a surface of the base material.
In order to process a surface of a magnetic garnet single crystal film or remove unnecessary magnetic garnet single crystal film from the base substrate in the process for manufacturing a device such as an optical isolator or the like, a method is conventionally used in which the garnet single crystal film is mechanically processed or a protecting film of polyimide or the like is formed, and then a portion of the magnetic garnet single crystal film, which has no protecting film, is removed by etching with hot phosphoric acid.
However, the conventional method of mechanically processing or removing by etching has a problem in that it is difficult to control the thickness. In the etching method, the nonmagnetic garnet substrate used as the base substrate is also etched to cause variation in the thickness of the base material, thereby causing a problem in that it is difficult to design a device utilizing a dielectric material of a base material.
In view of the foregoing, the present invention provides a method of producing a magnetic garnet single crystal film which is capable of growing a magnetic garnet single crystal film and, at the same time, providing the grown magnetic garnet single crystal film with any desired shape and thickness. The present invention also provides a magnetic garnet single crystal film grown on a surface of a substrate which has a nonuniform thickness immediately after film growth.
In order to achieve the objects, a method of producing a magnetic garnet single crystal film by the liquid phase epitaxial process, comprises the steps of: forming a platinum or platinum alloy film in any desired shape having any desired thickness on a nonmagnetic garnet single crystal substrate; and bringing the nonmagnetic garnet single crystal substrate into contact with a magnetic garnet raw material melt containing lead oxide as a flux to grow the magnetic garnet single crystal film on the nonmagnetic garnet single crystal substrate while removing the platinum or platinum alloy from the nonmagnetic garnet single crystal substrate with the flux.
A magnetic garnet single crystal film of the present invention is grown on a nonmagnetic garnet single crystal substrate while removing platinum or platinum alloy previously formed on the nonmagnetic garnet single crystal substrate, allows the thickness of the magnetic garnet single crystal substrate to be nonuniform on a surface of the nonmagnetic garnet single crystal substrate, if desired.
As seen from the above description, the method of producing magnetic garnet of the present invention can grow a magnetic garnet single crystal film, and at the same time, provide the grown magnetic garnet single crystal film with any desired shape and thickness. A magnetic garnet single crystal film grown to nonuniform thickness on a surface of a substrate can be obtained. The production method can eliminate the etching process for removing a magnetic garnet single crystal film after growth.